As is well known, screws can have heads with various design configurations. Two of the most common screw head types or designs are: those having a single straight slot and those having two slots that cross at about their centers. As used herein, a screw having a single straight slot in its head is called a "standard" screw and a screw having two crossing slots is called a "PHILLIPS" head or cross-slotted screw. "PHILLIPS" is a trademark of Phillips Screw Company of Natick, Mass.
A "PHILLIPS" head or "PHILLIPS" type screwdriver is required for installing and removing such a "PHILLIPS" screw while, on the other hand, a standard screwdriver, i.e., one having a single straight blade, is required for installing and removing such a "standard" screw. Thus, a workman must take both standard and "PHILLIPS" screwdrivers with him to the job site because he can never be sure which type of screw fastener he will encounter. He may, in fact, encounter both types.
Thus, there is a need for an economical and practical screwdriver that can be used for installing and removing both "PHILLIPS" type and "standard" screws.
One attempt to solve this problem has been to provide a screwdriver with a single shaft having a "PHILLIPS" type tip on one end, a flat blade on the other end, and a handle in about the middle.
Such a screwdriver may not be desirable, however, because the handle is not positioned for optimum effectiveness when either installing or removing a screw. For instance, it may not be possible for a workman to exert a desired amount of force along the shaft axis when using the above described screwdriver because of the handle position. Additionally, screwdrivers having this design are not as convenient as desired because presently available tool belts do not accommodate them.
Another attempt to solve the problem has been to provide a screwdriver having a single handle with a plurality of removable tips of different designs. Thus, for example, one of such tips can be used for "PHILLIPS" type screws, while another one of the tips can be used for "standard" screws.
This may not be satisfactory, however, because the removable tips can be misplaced and lost. Additionally, the mechanism for holding the tips in the handle can be fairly cumbersome and it can take longer than desired to switch from one style of tip to another.
There are also several U.S. patents which disclose screwdrivers designed for use on more than one style of screw fastener. For example, U.S. Pat. No. 2,116,775 to G. P. Blackburn discloses a screwdriver which ". . . may serve either in the capacity of an ordinary screwdriver applicable for single straight slotted screws, or for use with screws having cross-shaped slotted heads." Blackburn discloses that his device comprises four separate bits which are movable relative to each other and which can either be useful for operating on a single slot or cross-slotted screw. All four bits are mounted in and extend from the screwdriver handle. When the bits are fully extended, they form a cross and thus can engage a cross-slotted screw. When, however, a screw having a single slot is encountered, two of the bits opposite from each other can be moved into the handle a greater distance than the other two bits so that the bits that remain fully extended form a single "blade". These two bits or single "blade" can then engage the slot of the single slot screw.
When a screwdriver is used which has a design similar to that disclosed by Blackburn, the same bits that are used for straight slotted screws are also used for cross-slotted screws. This may not be desirable because normally the slot in a "standard" screw is shaped differently from either of the slots in a cross-slotted screw. For instance, normally the slot in a "standard" screw is flat at its bottom while the slots in a "PHILLIPS" type screw taper toward the center of the screw. Therefore, the bits or blades of a device similar to that of Blackburn are not optimally shaped for best engagement with both screw types. Additionally, it is disclosed that a pin must be removed and reinstalled each time the bits are moved to a different position. This can take an undesirable amount of time and there is a possibility that the pin can be lost. Further, since the bits are not fixed permanently in the handle, the bits can be lost.
U.S. Pat. No. 2,522,996 to J. H. Cone discloses a ". . . universal screwdriver having bit means adapting it for use with either slotted or recessed screw heads." The screwdriver disclosed by Cone has an integral blade suitable for use with conventional slotted head type screws. An adapter bit designed for use on various types of recessed head screws can be mounted onto the conventional blade.
Thus, since the adapter bit disclosed by Cone is not permanently connected to the screwdriver, there is the possibility that it can be lost.
U.S. Pat. No. 3,674,070 to Mahoney discloses a hand tool having the capability to engage various types and sizes of screw fastener heads. The hand tool disclosed in this patent comprises a bundle of wires held in a generally tubular housing with one end of the bundle projecting slightly beyond the end of the housing. The other end of the bundle presses against a deformable cell located in the housing. A handle is attached to the other end of the housing. When the projecting wires are pressed against the head of a screw fastener, the wires deform, making a replica mold of the surface of the screw head, wherein some of the wires move into the slot or slots in the head. Thus, a "blade" comprising a plurality of wires extends into either the single slot of a "standard" screw or the cross-slots of a "PHILLIPS" type screw.
There remains a need in the art, however, for an economical, easy to use, reliable screwdriver that has both a single blade specifically designed for use on a "standard" screw and additionally a "PHILLIPS" head tip for use on a "PHILLIPS" or cross-slotted screw, where all of the screwdriver components are permanently connected together.